[Nsi-wg] Feedback for WS protocol

[Guy Roberts]

Hello Henrik,

Welcome to the NSI discussions, here are some thoughts on your feedback:

1. the four messages described are not as illogical as they first appear.  Please be aware that there can be a long delay between a reserveRequest and reserveConfirmed/failed  so a quick acknowledgment of the receipt of the reserveRequest is useful.

2. In general I agree that the pathObject does not fit well with the serviceParameters

3. I will check and make sure these are made consistent

4&5. I have not strong feeling on this point - others may like to comment.

Guy 



-----Original Message-----
From: nsi-wg-bounces at ogf.org [mailto:nsi-wg-bounces at ogf.org] On Behalf Of Henrik Thostrup Jensen
Sent: 13 July 2011 12:17
To: NSI Working Group
Subject: [Nsi-wg] Feedback for WS protocol

Hi everyone

(I'm the NORDUnet developer creating the OpenNSA NSI implementation).
(Also, please ignore a potential double post due to wrong sender email)

I have some feedback/changes/wishes/questions for the WS-rendering of the 
NSI protocol.

1. Odd request/reply structure.

The request/reply structure is somewhat odd. It seems that for every 
request there is an message to imply that the message itself has been 
received as well as the actual response, which also has a response. I.e., 
the interaction will look like this for a reservation (AFAICT)

A -> B: reserveRequest
A <- B: reserveResponse
A <- B: reserveConfirmed
A -> B: reserveConfirmedResponse

This means that 4 messages are exchanged, when 2 would be enough. This is 
silly in my opinon, and only adds complexity to the implementation without 
adding any value. Also, at some point in time the reserveResponse and 
reserveConfirmed will get reordered as they don't have any ordering 
between them, meaning the requester will have to understand that case. It 
also seems to against the spec, which defines the primitives 
reserveRequest, reserveConfirmed, and reserveFailed.


2. Moving pathObject out of ServiceParameters

I would very much like to move pathObject out of serviceParameters and 
into the top-level attributes. As a reservation is created the pathObject 
send around changes, where as the rest of the ServiceParameters does not. 
This also reflects itself in data structures where this becomes somewhat 
backwards to keep track of the path in aggregate connections. It is of 
course completely possible to keep the current structure, but it would 
simplify the implementation to move the path out of the service 
parameters.

Also: Rename pathObject to path everywhere. We do not put the object 
suffix on other things either.

Also(2): Rename OrderedStpListType to StpListType in spec. and protocol. A 
list is by definition ordered, otherwise it would be called a multiset or 
bag.


3. Protocol service parameters differ spec service parameters

In the spec. schedule is in service parameters, in the WS protocol it is 
in the ReservationRequestType. I don't have any strong opions on where it 
should be, but I think it should be consistent.

Somewhat similarly the spec. has guarenteed and preferred under 
serviceAttrs (which is under ServiceParameters). In the WS protocol 
guaranteed and preferred are directly under ServiceParameters. Again I 
don't have any strong opions on what is correct, but I think it should be 
consistent.


4. The transactionId

The transactionId is not mentioned in the spec., but is used to denote 
session due to SOAPs lack of it. Could we call it something less 
misleading? It has nothing to do with transactions. E.g., sessionId, 
requestId (i prefer the latter as a session could technically consist of 
several requests).


5. Inconsistent path description

The spec. introduces the notion of a service demarcation point as a pair 
of connected STPs. Could we introduce this type (essentially a 
tuple/struct/complextype with two STPs), and use it for describing paths, 
such that a path is a (sourceSTP, destSTP, SDPList).


     Best regards, Henrik

  Henrik Thostrup Jensen <htj at ndgf.org>
  NORDUnet / Nordic Data Grid Facility.
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